In certain types of aircraft, turbine engines are mounted to pylons depending from the aircraft wings. Generally, fore and aft mounting bracket assemblies and auxiliary structures connect the engine to the pylon in a manner that accommodates a variety of engine mounting requirements, such as thrust reaction, torque reaction and a variety of static and dynamic loading conditions. The mounting brackets also encounter severe operating conditions, especially vibrations and high temperatures in the case of the aft brackets. An example of a desirable aft turbine engine mounting bracket is disclosed in U.S. Pat. No. 4,805,851 issued on Feb. 21, 1989 to Herbst and owned by the assignee of the present application.
To accommodate the vibrations so as to isolate the aircraft cabin from the engine noise, there is provided in the Herbst mounting bracket an elastomeric bearing assembly. Such a bearing assembly comprises a laminated structure including layers of elastomeric material alternating with shims of metal at predetermined locations. The laminate extends horizontally along a torque tube and is held by a rigid cap fastened to a base plate which, in turn, is mounted to the underside of the wing pylon. A pair of engine mounting arms extend horizontally in spaced parallel relation from opposite ends of the torque tube for connection to an engine hanger. The upper horizontal metal member of the laminate is in contact with the base, and the lower horizontal metal member of the laminate is in contact with the casing. The elastomeric layers are generally pre-compressed. Thus, as the bearing assembly heats up in use, stresses build-up in the elastomeric layers. With wide temperature variations, sizable stresses develop, resulting in reduced life, ruptures, looseness and excessive drift. This necessitates overhaul and replacement of the bearing.